How to use this.skip() from different exports function

I am using mocha to run tests, I want to skip the test programatically. I came across this.skip(). I want to skip the test based on condition but I am seeing error 'TypeError: this.skip is not a function'

Also I am not this.skip(), here this refers to which object?

This is my spec file

test.spec.js

const expect = require('chai').expect;
const Mochaexport = require('../cypress/support/mochaExport');
let mochaExp = new Mochaexport(); 

describe('mocha test', function() {
    it('runs mocha test', function() {
        mochaExp.skipTest("2020");
        expect(true).to.equal(true);
    })
})

mochaExport.js

const { expect } = require("chai");

module.exports = function() {

    this.skipTest = function(Year) {
        if(Year == "2020") {
            this.skip();
        } else {
            expect(Year).to.equal(2021);
        }
    }
}